1. Field of the Invention
The present invention is directed to methods for improving semiconductor devices and, in particular, to methods and apparatuses for the detection and reduction of dielectric breakdown in such devices.
2. Background Art
In general, the gate oxide thickness for the current generation of field-effect transistors (FET) is approximately 50 Angstroms. The next generation of FETs will require thinner oxides in order to achieve desired miniaturization. However, with current technology the electron current that would leak through a thinner gate oxide during transistor usage would be too large to prove useful. In fact, such large leakage currents would likely lead to permanent damage of the oxide layer, potentially damaging the FET in minutes. These leakage currents are thought to be due to dielectric breakdown in the insulating layers. This makes dielectric breakdown a critical issue in the miniaturization of FETs and other semiconductor devices. Yet, little, if anything, is understood about the mechanism responsible for dielectric breakdown in thin dielectric layers in electronic devices.
It is known the operating electric field increases as the dielectric thickness decreases. The electric field is the ratio of the applied voltage across the dielectric and its thickness. If the thickness is reduced by a factor of 2, then one could maintain exactly the same electric field by reducing the applied voltage by the same factor of 2. Unfortunately, one cannot scale the gate voltage down proportionally to the thickness because the voltage becomes too small to control the current across the FET between the source and drain. Thus, thinner dielectrics must operate with higher electric fields.